1. Field of the Invention
This invention relates to compositions useful as lubricants for spotting fluids in well drilling operations with either oil-based or water-based muds. The compositions of the invention are non-toxic and biodegradable, are especially useful in fast hole drilling, and also function as performance extenders for corrosion inhibitors in high velocity gas, oil or water drilling, production or gathering applications. The invention also relates to a method for making the subject lubricant using a controlled mixing process and distillation under controlled conditions to remove more volatile components and promote esterification and further reaction with amine substituents.
2. Description of Related Art
International Publication No. WO 97/12947, which claims priority based on U.S. Ser. No. 08/538,262, filed Oct. 3, 1995, discloses high flash point, low vapor pressure, cleaning compositions for oil and gas wells, said compositions containing about 40 to 99 weight percent of a fatty acid alkyl ester blend and about 1 to 25 weight percent of at least one lower alkyl glycol ether. The disclosed compositions, when injected into wells, are said to produce a coating on well casings, lines, pumps, pipes and other equipment, to prevent the adhesion and accumulation of paraffins, other related soils, and scale on these parts to help retard corrosion, and to allow more efficient operation and consistent production between cleanings. Preferred fatty acid alkyl ester blends for use in the invention are selected from the group consisting of C.sub.1 to C.sub.8 esters of C.sub.4 to C.sub.22 fatty acids. Preferred lower alkyl glycol ethers are selected from the group consisting of ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl either, and mixtures thereof. The optional use of from 1 to 40 weight percent polyoxyalkylene glycol ethers is also disclosed.
Various other prior art drilling fluid additives, spotting fluids and lubricant compositions are disclosed, for example, in U.S. Pat. Nos. 2,500,163; 3,108,068; 3,298,954; 3,396,105; 4,263,465; 4,282,392; 4,436,636; 4,464,269; 4,502,963; 4,525,285; 4,587,368; 4,652,385; 4,876,017; 5,421,907; and 5,547,925.
A well lubricant composition is needed that has a low acid number, and is therefore much less likely to form calcium soaps from lime in downhole formations, which can in turn cause undesirable foaming in drilling muds. The desired composition should also be nontoxic and not susceptible to foaming during manufacture.